int trigPin = 2;
int echoPin = 3;




void setup() {
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  Serial.begin(9600);
  

}

void loop() {
  digitalWrite(trigPin,LOW);
  delayMicroseconds(5);
  digitalWrite(trigPin,HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin,LOW);

 long time = pulseIn(echoPin,HIGH);
 

 int centi = time/2/29.1;
 //float centi = time/2*0.0343;
 //Serial.println(centi);

  // int inch = time/2/74;
  //float inch = time/2*0.0135;
  //Serial.println(inch);

 if (centi < 10){
  digitalWrite(13, HIGH);
 }
 else{
  digitalWrite(13, LOW);
 }


}